Method for clamping platens of injection molding machines

ABSTRACT

An securing/clamping assembly for clamping platens of an injection molding machine includes a mechanism for guiding the platens and a body member having a structure which is movable as a single unit. The body member is adapted to be attached with at least one of the platens and includes a mechanism for securing the mechanism for guiding and for conveying a clamping force to the platens for clamping the platens during injection molding. The mechanism for securing includes an engagement mechanism for placing the mechanism for securing into and out of locking engagement with the mechanism for guiding, such that when the engagement a mechanism is out of locking engagement with the mechanism for guiding, the body member and the mechanism for guiding are relatively movable.

This is a Continuation of application Ser. No. 08/482,870, filed Jun. 7,1995, now U.S. Pat. No. 5,645,875.

BACKGROUND OF THE INVENTION

This invention is directed to injection molding machines, and moreparticularly, to an securing and clamping assembly for use with the barsof both singular and tandem injection molding machines.

The prior art includes many types of tie bar gripping and clampingassemblies for use with injection molding machines. The gripping of thebars via these assemblies allows for a high clamping force to be appliedto the mold halves during injection molding. Typical tie bar grippingand mold clamping mechanisms are shown in the patents to Fukuzawa etal., U.S. Pat. No. 5,135,385; Romi, U.S. Pat. No. 5,275,550; Hirata,U.S. Pat. No. 5,238,394 and Kushibe et al., U.S. Pat. No. 4,874,309. Ineach of these patents, a combination tie bar gripping mechanism moldclamping unit is disclosed wherein the tie bar is gripped via clampingdevices moving transverse the longitudinal direction of the tie bars.

Accordingly, with reference to FIG. 5, Romi discloses the use ofhydraulic clamps 9 and 10 for engaging circular grooves 18 of tie bar 17for gripping the tie bars prior to the application of a clampingpressure via separate hydraulic cylinders 7. Similarly, Kushibe et al.discloses the use of halves 180 for clamping threads 172 of tie bar 164so as to grip the tie bars prior to the application of a clamping forcevia separate hydraulic cylinders 160.

More particularly, the patent to Fukuzawa et al. discloses a clampingsystem which includes a fixed platen on one end of a machine base and aplurality of clamping cylinders wherein the fixed platen holds a fixedmold therein. A movable platen is fixed to the other end of the machinebase and holds a movable mold therein, wherein a plurality of tie barsextend through the movable platen into the fixed platen. At one end ofthe tie bars, pistons are positioned wherein the pistons are slidablyreceived within the clamping cylinders. In addition, the tie barsinclude screw threads or grooves on their end nearest the clampingcylinders. A unit is disposed between the movable platen and the fixedplaten for moving the movable platen to and from the fixed platen. Themovable platen includes two part nuts mounted therein for meshinglyengaging additional screw threads or grooves positioned adjacent the endof the tie bar nearest the movable platen.

A further stopper mechanism is included in the movable platen which isengagable with recesses on the tie bars. The inner peripheral surfacesof the pistons include threads which are engageable with the screwthreads or grooves on the tie bars adjacent the fixed platen.Accordingly, the pistons may be rotatable through means connected with adrive while engaged with the threads or grooves of the tie bars foradjusting the clamped position of the mold halves. Clamp position isadjusted by maintaining the female screw on the inner surface of thepiston in meshed relationship with the screw portion at the end of thetie bar. By rotating the piston via a mechanism such as a sprocket andchain, the position of the mold halves can be adjusted as necessary. Forthis design, the threads on the inner surface of the piston are alwaysmaintained in meshed relationship with the threaded end of the tie barand are used primarily for shut height adjustment.

Hirata discloses a mold clamping apparatus for a molding apparatus. Themold clamping apparatus includes a base, a fixed panel and a movablepanel disposed on the base and respectively supporting mold halves. Aplurality of tie bars each having a screw shaft at one end thereof passthrough the movable panel toward the fixed panel. The plurality ofclamping cylinders are disposed on the fixed panel for clamping anotherend of the tie bars when the mold apparatus is in a closed position.Each clamping cylinder includes cylinders 14 and semi-circular chucks 17positioned transverse the longitudinal dimension of the tie bar. Thecylinders 14 are actuated for gripping tie bar upon contact of the tiebar with a recess positioned in a primary piston of the clampingcylinder. Once cylinders 14 are engaged with tie bars 9, pressure can beapplied to the primary piston 12 for providing the clamping force to themold halves 25. The clamping apparatus further includes a mechanism formoving the movable panel towards and away from the fixed panel and anadjusting mechanism disposed on the movable panel, for simultaneouslyfixedly adjusting the axial position of the screws on the tie bar withrespect to the movable panel so that molds of varying sizes can beaccommodated. The secondary clamping pistons 14 and semi-circular chucks17 are not rotatable into engagement with tie bars 9 and must bemaintained in engagement with the tie bars during the application ofpressure against primary cylinder 12.

The patents to Siegel, U.S. Pat. No. 3,183,555; Stubbe et al., U.S. Pat.No. 3,120,039 and Quere et al., U.S. Pat. No. 2,916,768 disclose furthertie bar clamping mechanisms for use with molding machines. Moreparticularly, Siegel discloses an expandable sleeve or bush 15 whichenvelopes the outer surface of a tie bar. The sleeve is adapted toengage inner walls of bores provided in a closing platen 9, wherein thebushes are adapted to receive guide columns or tie bars 4, such that theclosing platen 9 is held on the guide columns by frictional contact.Stubbe et al. discloses the use of cylinders 21 having pistons 23 whichare connected to levers 25 which in turn function to operate clampingjaws 26 for gripping shafts or tie bars 1. Quere et al. discloses theuse of pistons for operating claws which rotate to grasp mating claws oftie bars moving from a movable platen 4 to stationary platen 7. The jawsare located in the stationary platen. Finally, European Patent 0290858discloses the use of electromagnets 8 for clamping tie bar or columnends 7, for locking a movable tool clamping platen to a fixed toolclamping platen.

The patents to Schad et al., U.S. Pat. No. 5,185,119; Balevski et al.,U.S. Pat. No. 4,090,837 and Lohman, U.S. Pat. No. 3,707,342, disclosedifferent embodiments of tandem molding machines, i.e., wherein eachmachine has more than one mold. However, none of the tandem machinesinclude tie bar securing/clamping mechanisms as discussed above or asdisclosed in the present invention.

Schad et al. discloses an injection molding machine and method ofoperation having a plurality of accessory arrangements for molding aplurality of piece parts in efficient overlapping time cycle usingprimary and secondary molten plastic injection units, primary andsecondary clamping units, and a plurality of injection units in variousarrays including molding piece parts in reverse or uniform orientation.The tandem machine includes two fixed end platens and two center movablemold platens movable against and towards one of the fixed platens.

Lohman discloses a tandem injection molding apparatus having two molds,spaced apart with a dual nozzle injection unit positioned between themolds to fill the two molds alternately. The cooling periods of the twoclosed molds overlap in time and while one mold is cooling the other oneis opened, emptied of its molded part, closed again and injected with anew charge of plastic. During the cooling period of one mold, theinjection unit not only injects plastic into the other mold but alsorecharges for a new operating cycle. The machine includes a stationaryside platen and movable center and other side platens.

There exists, therefore, a need for an improved tie barsecuring/clamping assembly for use with single mold and tandem moldinjection molding machines, wherein the securing/clamping assembly canbe engaged and disengaged from the tie bar at each molding cycle.

SUMMARY OF THE INVENTION

The primary object of this invention is to provide an improved tie barsecuring and mold clamping mechanism for use with both tandem and singlemold injection molding machines.

Still another object of this invention is to provide a securing/clampingassembly for use with both tandem and single mold injection moldingmachines which provides the dual purpose of securing with tie bars andclamping mold halves closed for injection molding.

A still another object of this invention is to provide an improvedsecuring/clamping assembly for use in both securing tie bars andclamping mold halves for injection molding which is actuated viarotational movement.

The foregoing objects are achieved by the securing/clamping assembly ofthe present invention for clamping platens of an injection moldingmachine, which includes means for connecting the platens and a bodymember having a structure which is movable as a single unit. The bodymember is adapted to be attached with at least one of the platens andincludes means for securing the means for connecting and means forconveying a clamping force to the platens for clamping the platensduring injection molding. The means for securing includes engagementmeans for placing the means for securing into and out of lockingengagement with the means for connecting, such that when the engagementmeans is out of locking engagement with the means for connecting, thebody member and the means for connecting are relatively movable.

The details of the present invention are set out in the followingdescription and drawings wherein like reference characters depict likeelements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a simplified overhead view of a tandem injection moldingmachine having securing/clamping assemblies in accordance with theprinciples of the present invention;

FIG. 2 is an elevational view of the tandem injection molding machineshown in FIG. 1;

FIGS. 3a and 3b are detailed cross-sectional and end views of thesecuring/clamping assemblies in accordance with the principles of thepresent invention;

FIG. 4 is an end view of an injection molding machine in accordance withthe principles of the present invention showing the securing/clampingassemblies and rotational mechanism therefor;

FIG. 5 is an elevational view of a single mold injection molding machineincorporating the principles of the present invention;

FIG. 6a is an enlarged view of the rotational mechanism shown in FIG. 4in the disengaged position; and

FIG. 6b is an enlarged view of the rotational mechanism shown in FIG. 4in the engaged position.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to the drawings in detail, there is shown in FIG. 1, asimplified top view of a tandem injection molding machine designed inaccordance with the principles of the present invention and designatedgenerally as 10. Machine 10 generally includes a fixed center platen 12,a movable end platen 14, a movable end platen 16, an injection unit 18,tie bars 20 and 21 for guiding the movable platens and securing/clampingassemblies 22 and 23.

In this embodiment, center platen 12 is fixed to a base and movable endplatens 14 and 16 are movable away from and toward center platen 12 viapositioning cylinders 25 and 27, respectively, as shown in FIG. 2.Center platen 12 includes a molding side 24 having a first stationarymold half 26 and a molding side 28 including a second stationary moldhalf 30. In addition, center stationary platen 12 includes a first hotrunner 32 for directing melt to first stationary mold half 26 and asecond hot runner 34 for directing melt to the second stationary moldhalf 30. Locking flanges 36a and 36b extend from the side of the fixedcenter platen for alternating engagement with injection unit 18.Alternatively, a single fixed connection could be used with adistribution valve to feed resin to either side of the center platen andrespective mold. Movable platens 14 and 16 each include a movable moldhalf 29 and 31, respectively, for forming molds upon closing withstationary mold halves 26 and 30, respectively.

Referring to FIG. 1, and FIG. 2 showing an elevational view of machine10 shown in FIG. 1, tie bars 20a-20d (20c not shown) extend from fixedcenter platen 12 toward movable end platen 14 and four tie bars 21a-21d(21d not shown) extend from fixed center platen 12 toward movable endplaten 16. Tie bars 20a-20d and 21a-21d are arranged at the corners ofthe fixed center platen 12 such that when the mold is closed, theyextend through securing/clamping assemblies 22a-22d (22c not shown) and23a-23d (23d not shown), respectively, carried by, or within the movableend platens 14 and 16, respectively. The tie bars are preferablystationary while the movable platens move relative thereto and aresupported on guide shoes such as shoe 33a shown in FIG. 3a.

Each of end platens 14 and 16 include four bores shown by dotted linesin FIGS. 1 and 2, 35a-35d (35c not shown) and 37a-37d (37d not shown),respectively, in which clamping and securing assemblies 22a-22d and23a-23d, respectively, extend. Movable platen 14 and 16 preferablyinclude fasteners, shown in FIG. 4, on the outwardly facing surfacethereof for the securement of the securing/clamping assemblies,respectively.

The securing/clamping assemblies function to both grip or engage the tiebars and apply pressure to the mold halves during mold injection.Accordingly, from a general standpoint, each of the securing/clampingassemblies 22a-22d and 23a-23d include a mechanism for securely andpositively engaging the tie bar, wherein the mechanism is furthercapable of conveying pressure to the platens for forcing the mold halvestogether during injection molding. Preferably, each securing/clampingassembly is formed from a body member having a structure which ismovable as a single unit for securing with the tie bars and applyingclamping pressure between the platens.

All of the securing/clamping assemblies, bores, and the tie bars aresubstantially the same and accordingly, only one securing/clampingassembly 22a, bore 35a and tie bar 20a are described in detail alongwith their associated elements, it being understood that the descriptionapplies equally to all securing/clamping assemblies, bores and tie barsand associated elements.

In a particular embodiment of the securing/clamping assemblies,securing/clamping assembly 22a is mounted on the outwardly facing sideof movable end platen 14 and within bore 35a as shown in FIG. 1, and asdiscussed above. Referring to FIGS. 3a and 3b, in order for thesecuring/clamping assembly 22a of platen 14 to function with tie bar20a, tie bar 20a includes an elongated end section having a plurality ofspaced protrusions in the form of teeth 38a separated by longitudinallyextending inner slots 40a, as shown in FIG. 6a. Accordingly, at the endof tie bar 20a is a toothed outer surface, as shown in FIG. 3a. Thetoothed outer surface of tie bar 20a is in the form of longitudinalouter strips of teeth 39a extending in the axial direction of the tiebar, wherein the teeth 38a are preferably aligned in a radial directionon the tie bar and separated by a space in the axial direction. Each ofthe strips of teeth such as strips of teeth 39a and 39b are radiallyseparated from another strip of teeth via an outer axially extendingslot, such as slots 40a and 40b. Outer strips of teeth 39a and slots 40aof tie bar 20a are adapted to engage and align, respectively, with innerteeth and grooves of securing/clamping assembly 22a, discussed below, inorder to cause a locking engagement with the bar 20a.

Securing/clamping assembly 22a is positioned in bore 35a and is securedtherein via retaining ring 41a, seals 63a and fasteners 42a, as shown inFIG. 3a. Securing/clamping assembly 22a is comprised of a member in theform of a piston 44a adapted to be positioned in bore 35a and coaxiallyrelative to a tie bar 20a, as shown in FIGS. 3a and 3b. Piston 44aincludes an outer surface 46a and an inner surface with axiallyextending teeth 48a separated by spaces in the axial direction, whichare adapted to engage teeth 38a of the strips of teeth 39a of tie bars20a. A slight axial clearance is provided between the teeth 38a of tiebars 20a and the inner teeth 48a of toothed piston 44a to allow forrelative movement and position error adjustment during engagement of theteeth. In FIG. 3a, the top half of the figure shows locking engagementof teeth 38a of tie bar 20a with inner teeth 48a of piston 44a, and theclearance, while the bottom half shows non-engagement. Inner teeth 48aare included in a plurality of equally radially spaced and axiallyextending inner strips of teeth, such as 49a, which are radiallyseparated from each other by inner slots 51a, as shown in FIG. 6a andaxially separated by a space.

In order to achieve relative motion between securing/clamping assembly22a and tie bar 20a, outer strips of teeth 39a of tie bar 20a are lessin radial width than inner slots 51a of piston 44a and outer slots 40aof tie bar 20a are greater in radial width than inner strips of teeth49a of piston 44a, thus allowing sufficient space for axial movementtherebetween. During engagement or disengagement of strips of teeth 39awith strips of teeth 49a, teeth 38a do not extend into the spacesbetween teeth 48a or slots 51a, respectively, the entire depth of thespaces or slots thereby leaving a clearance between the teeth and pistonbore. A clearance also preferably exists between teeth 48a and theinnermost surfaces of tie bar 20, i.e. the surfaces defined by thespaces between teeth 38a or the surface of slots 40a.

Outer surface 46a of piston 44a has a stepped shape preferably includinga base portion 50a having a wider diameter than a neck portion 52a. Bore35a is shaped to closely receive piston 44a at the base and neckportion. Accordingly, bore 35a has a smaller bore portion 54a having adiameter only slightly greater than the diameter of neck portion 52a andlarger bore portion 56a having a diameter only slightly greater than thediameter of base portion 50a of piston 44a. Smaller bore portion 54a andlarger bore portion 56a are circular in shape and are separated by anintermediate bore portion 58a having a hemispherical, tapered, steppedor other type of shape, the choice of which is not critical.Intermediate bore portion 58a begins at smaller bore portion 54a,expanding outwardly to its maximum diameter just prior to larger boreportion 56a. The maximum diameter of intermediate bore portion 58a isless than the outside diameter of larger bore portion 56a, and baseportion 50a of piston 44a. Accordingly, a face 60a is formed betweenintermediate bore portion 58a and larger bore portion 56a against whichaxially transverse surface 62a of piston 44a can abut.

Referring still to FIGS. 3a and 3b, seals 64a are provided betweensmaller bore portion 54a and neck portion 52a and seal 69a is providedbetween larger bore portion 56a and base portion 50a of piston 44a.Intermediate bore portion 58a is accordingly greater in diameter thanthe transitional area 59a between base portion 50a and neck portion 52a,defined in part by axially transverse surface 62a, of piston 44a.Accordingly, free space 66a is provided between bore 35a and piston 44ain the vicinity of the intermediate bore portion 58a. This space 66a isappropriately sealed via seals 64a and 69a, for the introduction ofpressurized air, hydraulic or other fluid in order to provide a clampingpressure against surface 62a of piston 44a for pressing the movableplaten 14 against the fixed center platen 12 during injection molding.Clamping pressure is released by releasing hydraulic pressure from space66a and applying hydraulic fluid under pressure in cavity 65a againstsurface 67a of piston 44a. Before pressure is applied in space 66aagainst surface 62a so as to force movable platen 14 against the fixedcenter platen 12, inner strips of teeth 49a of piston 44a should firstbe engaged with outer strips of teeth 39a of tie bar 20a. Such lockingengagement, and disengagement, of inner strips 49a with outer strips 39ais accomplished via rotational mechanism 68, shown in FIG. 4.

Rotational mechanism 68 is used for rotating securing/clampingassemblies 22a-22d and is substantially the same as the rotationalmechanism (not shown) used with securing/clamping assemblies 23a-23d.Accordingly, only rotational mechanism 68 is described in detail, itbeing understood that the description applies equally to the rotationalmechanism used with securing/clamping assemblies 23a-23d.

As shown in the end view of FIG. 4 where securing/clamping assemblies22a-22d are shown positioned in movable platen 14, rotational mechanism68 is preferably in the form of a linkage assembly which extends betweenand is connected to all four securing/clamping assemblies 22a-22d on themovable end platen 14. Rotational mechanism 68 specifically connectssecuring/clamping assemblies 22a and 22b and securing/clampingassemblies 22c and 22d. The linkage assembly of rotational mechanism 68includes one or more, preferably a pair, of piston/cylinder mechanisms70 and 71 attached to bracket 72 between two of the securing/clampingassemblies, i.e. securing assemblies 22a and 22c.

Both piston/cylinder mechanisms 70 and 71 and associated linkage aresubstantially the same and accordingly only one piston/cylinder assembly70 and associated linkage will be described in detail, it beingunderstood that the description applies equally to assemblypiston/cylinder assembly 71 wherein assembly 71 is substantially themirror image of assembly 70.

The non-moving end of piston/cylinder assembly 70 is pivotally attachedto bracket 72 and piston rod end 73 of piston/cylinder assembly 70extends toward securing/clamping assemblies 22a-22b.

Piston rod 73 extends from piston/cylinder assembly 70 and is attachedvia a bearing assembly 76 to the end 77a of piston 44a. Linkage arm 80is attached to bearing assembly 76 which pivots about stud 78 fastenedto end surface 77a. Linkage arm 80 traverses a portion of end 77a ofpiston 44a and is connected at another stud 82 on end 77a. Studs 78 and82 are preferably spaced from each other on the end surface 77a ofpiston 44a, approximately 90°. Stud 78 is preferably positioned on theouter side 83 of the vertical centerline of securing/clamping assembly22a. A second linkage arm 84 extends from stud 82 which connectssecuring/clamping assemblies 22a and 22b and is attached to the endsurface 77b of piston 44b. Linkage arm 84 is pivotally attached tosecuring/clamping assembly 22b at a stud 86, wherein stud 86 ispositioned on securing/clamping assembly 22b adjacent the outer side 87of the vertical centerline of securing/clamping assembly 22b.

The dotted lines in FIG. 4 indicate movement of rotational mechanism 68upon the actuation of piston/cylinder assemblies 70 and 71. The solidlines show the pistons in the unextended position with the inner stripsof teeth 49a-49d of the pistons 44a-44d being unengaged with outerstrips of teeth 39a-39d of tie bars 20a-20d. The dotted lines of thesecuring/clamping assemblies also show the inner strips of teeth 49a-49dof pistons 44a-44d engaged with the outer strips of teeth 39a-39d of tiebars 20a-20d. This engagement and disengagement is shown in more detailin FIGS. 6a and 6b, where FIG. 6a shows the securing/clamping assembly22d in the disengaged position, i.e. teeth 39d and 49d unmeshed and FIG.6b shows the securing/clamping assembly 22d in the engaged position withteeth 39d and 49d meshed. Accordingly, upon simultaneous actuation ofpiston/cylinder assemblies 70 and 71, inner strips of teeth 49a-49d,securing/clamping assemblies 22a-22d, respectively, can be synchronouslyengaged and disengaged with outer strips of teeth 39a-39d of tie bars22a-22d, respectively, so as to lock movable platens 14 and 16 intosubstantially closed positions prior to the application of the desiredclamping force via pressure against surfaces 62a-62d (62b-62d not shown)of pistons 44a-44d (44b-44d not shown), as shown in FIG. 3a.

The total available travel of piston 44 is at least the total of thepitch of the strips of teeth plus the clearance plus the maximumelongation of the tie bars. This allows shut height to be adjusted toany point between maximum and minimum even though engagement between tiebar teeth and piston teeth is of a fixed pitch.

While the rotational mechanism 68 has been described in detail as alinkage assembly, it is to be understood that other types of rotationalmechanisms can be used such as, for example, sprockets, belts andchains, directly synchronized drives, and rack and pinion assemblies.

While the securing/clamping assemblies 22 of the present invention havebeen described for use with a tandem injection molding machine having afixed center platen and two movable end platens, the securing/clampingassemblies are by no means limited to such use. Assemblies 22 can beincorporated in a manner similar to as described above for tandem typemachines having a fixed end platen and movable platens movable towardthe fixed end platen. Use of the securing/clamping assemblies is alsofeasible and contemplated for other variations of tandem machines.

Further, the securing/clamping assemblies can be equally used with anon-tandem machines 110, as shown in FIG. 5, i.e. injection moldingmachines having a single stationary mold platen 114 and one movableplaten 112 or any other variation thereof. Accordingly, FIG. 5 isindicative of the use of the securing/clamping assemblies 22, thereinassemblies 122, of the present invention with a non-tandem machine 110.The above description of the securing/clamping assemblies, rotationalmechanisms, and the additional parts of the injection molding machine,are equally applicable to a non-tandem machine and is incorporatedherein. Alternatively, assemblies 122 can be mounted on fixed platen 114and tie bars attached to moving platen 112.

Referring now to FIGS. 1-4, and 6 the operation of the injection moldingmachine 10 in accordance with the principles of the present inventionwill be described. For the sake of simplicity, multiplesecuring/clamping assemblies and associated elements and multiple tiebars and associated elements will be referred to by number designationonly and not the letter designations, unless otherwise noted.

In operation of tandem machine 10 as shown in FIGS. 1 and 2, rotationalmechanism for each movable platen 14 and 16, as shown in FIG. 4, is setsuch that the plurality of securing/clamping assemblies 22 and 23,respectively, are unengaged with tie bars 20 and 21, respectively, i.e.wherein the slots of the tie bars and securing/clamping assemblies arein alignment with the teeth of the securing/clamping assemblies and tiebars, respectively, thus allowing movement of movable platens 14 and 16relative the tie bars and center fixed platen 12, as shown in FIG. 6a.By way of example only, movable platen 14 is first moved into the moldclosed position as shown in FIG. 2, while movable platen 16 remains in amold open position as also shown in FIG. 2. In achieving the mold closedposition of the mold halves 26 and 29, as shown in FIG. 2, movable moldhalf 29 is moved via positioning cylinder 25 into engagement with firststationary mold half 26. In addition, injection unit 18 is locked inengagement with locking flange 36 of first hot runner 32, as shown bythe dotted lines of FIG. 1 or alternatively, a distribution valve isused to direct flow to mold halves 26 and 29. Accordingly, duringmovement of movable end platen 14, rotational mechanism 68 for movableplaten 14 is in the position as shown by the solid lines in FIG. 4. andsecuring/clamping assemblies 22 are movable relative to tie bars 20.

When first stationary mold half 26 and first movable mold half 29 are inthe position shown in FIGS. 1 and 2, rotational mechanism 68 is actuatedvia piston/cylinder assemblies 70 and 71 such that the inner strips ofteeth 49a of pistons 44a are rotated into engagement with outer stripsof teeth 39a of tie bars 20. The initial position of the mold halves isachieved by moving the movable platen in a stepwise manner until stripsof teeth 39a and 49a are in position for engagement. The engagedposition of the rotational mechanism 68 is represented by the dottedlines shown in FIG. 4. Such engagement of strips 39a of tie bar 20a withinner strips of teeth 49a of pistons 44 is also shown in the upper halfof FIG. 3a and in FIG. 6b.

With the inner strips 49a engaged with outer strips of teeth 39a and thefirst stationary mold half 26 being positioned in molding engagementwith first movable mold half 29, pressure can be applied to the moldhalves via the securing/clamping assemblies 22.

Accordingly, referring again to FIG. 3a, hydraulic pressure or the likeis provided in bore 37a against longitudinal transverse surfaces 62a ofeach securing/clamping assembly 22. The hydraulic pressure againstsurface 62a forces first stationary mold half 26 and first movable moldhalf 29 sealably together in preparation for injection molding. As forcebetween the mold halves is maintained via each securing/clampingassemblies 22, melt is injected via injection unit 18 through first hotrunner 32 for facilitating molding. Once molding is complete, hydraulicpressure is removed from cavities 66a and is applied in cavities 65aagainst surfaces 67a of pistons 44a of securing/clamping assemblies 22,preferably using the axial clearance between the engaged teeth forslight relative movement, to break apart the molding halves. The surfacearea of surfaces 67a is smaller than the surface area of surfaces 62asince less force is required to break the mold halves. Once the moldhalves are broken apart, the teeth must be disengaged before mold halvescan be moved by cylinder 25 to the open position. Once disengagement ofthe teeth has been accomplished, positioning cylinder 25 moves the firstmovable mold half 29 away from first stationary mold half 26 so that themolded unit may be ejected by an ejection system 88 known in the art.

For the tandem machine 10 as shown in FIG. 1, as securing/clampingassemblies 22 are released and movable mold half 29 is moved to the openposition, the other movable mold half 31 is closed via cylinder 27, andclamped via securing/clamping assemblies 23, via the same operation asdiscussed above for mold halves 26 and 29 and securing/clampingassemblies 22, wherein injection unit 18 is moved into lockingengagement with locking flange 36 of second hot runner 34, or valvedirection is changed for injecting melt and forming a molded unit inmold halves 30 and 31. The securing/clamping assemblies 23 function inthe same manner as described above.

Mold halves 26, 29 and 30, 31 can be opened, closed, clamped andunclamped independently of each other. Each side of stationary platen 12can be operated as a completely independent machine or they can becoordinated and synchronized in any one of a number of ways.

FIG. 5 shows a single mold injection molding machine 110 havingstationary platen 114 and one movable platen 112. Injection moldingmachine 110 includes securing/clamping assemblies 122, similar to asdescribed above for the tandem machine, in movable platen 112, and isdesigned and functions the same as described above with regard tosecuring/clamping assemblies 22, tie bars 20 and rotating mechanisms 68,except only one set of securing/clamping assemblies, tie bars, and onerotating mechanism is used. Thus, FIG. 5 shows tie bars 120a and 120c,clamping and securing assemblies 122a and 122c, positioning cylinder125, mold halves 126 and 129, bores 135a and 135c for the tie bars,similar to FIGS. 1 and 2.

The primary advantage of this invention is that an improved tie barsecuring and mold clamping mechanism is provided for use with bothtandem and single mold injection molding machines. Still anotheradvantage of this invention is that an improved securing/clampingassembly is provided for use with both tandem and single mold injectionmolding machines which provides dual purpose of securing with the tiebars and clamping mold halves closed for injection molding. And stillanother advantage of this invention is that an improvedsecuring/clamping assembly is provided for use in both securing with thetie bars and clamping mold halves, for use with injection moldingmachines and which is actuated via rotational movement.

It is to be understood that the invention is not limited to theillustrations described and shown herein, which are deemed to be merelyillustrative of the best modes of carrying out the invention, and whichare susceptible of modification of form, size, arrangement of parts anddetails of operation. The invention rather is intended to encompass allsuch modifications which are within its spirit and scope as defined bythe claims.

What is claimed is:
 1. A method for clamping platens of an injectionmolding machine, which comprises:providing platens of an injectionmolding machine with mold halves connected thereto; connecting saidplatens with tie bars; securing said tie bars to at least one platen byan annular body member for each tie bar and attached to said platen,wherein each of said body members include a means for securing said tiebars and having a structure which is movable as a single unit; conveyinga clamping force to said mold halves by said body members, and conveyinga mold break force to said mold halves by said body members; placingsaid body members in and out of locking engagement with said tie bars byaligning engagement means of said means for securing so that when saidengagement means is out of locking engagement with said tie bars, saidbody members and said tie bars are relatively movable, including thestep of relatively rotating said body members and tie bars for placingsaid engagement means in and out of engagement with said tie bars.
 2. Amethod according to claim 1, including the step of placing said bodymembers in and out of locking engagement with said tie bars byengagement means of said means for securing which act independently ofsaid tie bars.
 3. A method according to claim 1, including the step ofplacing said body members in and out of engagement with said tie bars byengagement means of said means for securing cooperating with means forclamping on said tie bars which extend through at least one of saidplatens.
 4. A method according to claim 1, including placing said bodymember at least in part in a bore in at least one of said platens.
 5. Amethod according to claim 4, wherein said body member has an outersurface, and shaping the body member to form a cavity between the outersurface and said bore and to form surfaces extending substantiallytransverse to a clamping direction of said platens, and introducingpressured fluid into said cavity.
 6. A method according to claim 1,including engaging protrusions of said tie bars with said engagementmeans.
 7. A method according to claim 6, including engaging a firsttoothed surfaced of a tie bar with said engagement means.
 8. A methodaccording to claim 7, including the step of securing said tie bars to atleast one platen by at least one annular body member positionedcoaxially relative said tie bars, said body member including an innertoothed surface adjacent said tie bars, and including the step of matingsaid inner toothed surface with said first toothed surface.
 9. A methodaccording to claim 8, including rotating said body members into lockingengagement with said tie bars and engaging inner strips of teeth of saidtie bars with outer strips of teeth of said body members and aligninginner slots of said tie bars with outer slots of said body members. 10.A method according to claim 9, including the step of positioning thebody members at an intermediate position such that clearances areprovided between teeth prior to rotation into locking engagement.